Ferrous metals are used as coatings in many applications such as drill pipe hardbanding, mining truck bed liners, and boiler tubes, where the coatings provide wear and abrasion resistance to relatively less wear resistant components. These coatings can be applied to substrates via various techniques such as HVOF or twin-wire arc thermal spray, and PTAW or GMAW weld overlay.
Wear resistant ferrous metal coatings are generally characterized by a relatively low cost and a relatively high surface hardness which enables the wear resistance of the materials and protects the underlying substrate. The materials used as wear resistant coatings were designed to adhere to a substrate and provide the desired surface performance, and as such are largely dependent on the substrate for non-surface properties such as strength and toughness. Examples of ferrous metal coatings used for wear resistance include chrome carbides, complex carbides, titanium carbides, vanadium carbides, and tool steels.
Layerwise construction can be understood herein as a process where layers of a material are built up, or laid down, layer by layer to fabricate a component. Examples of layerwise construction include powder bed fusion with a laser (PBF-L) or electron-beam (PBF-E) energy source, directed energy deposition (DED), binder jetting (BJ), sheet lamination, material extrusion, material jetting, and vat photopolymerization. The primary layerwise construction processes used with metal include PBF-L, PBF-E, DED, and BJ.
Layerwise construction processes have excellent capability to construct components from a variety of ductile metals including stainless steel alloys, aluminum alloys, titanium alloys, nickel-based alloys, and cobalt chrome alloys. In liquid-phase layerwise construction processes for metals such as PBF-L, PBF-E, and DED, the construction material transitions from a solid phase to a liquid phase (melting), then back to a solid phase (solidification). The energy source used for melting can be focused to a relatively small area of the material surface to be melted and as such can control the volume of material being melted to a relatively small volume. The small molten volume, being in contact with a large solid volume, has the capability to solidify in a relatively rapid manner. This rapid solidification is responsible for grain size refinement and an increase in mechanical properties when compared to wrought metal properties.
While the mechanical properties of components constructed in this manner are generally relatively higher than wrought processes, none of the aforementioned materials possess the combination of relatively high hardness and wear resistance, and those with the highest hardness generally require heat treating processes such as quench and temper, or solutionizing and aging, to yield a relatively high hardness and wear resistance. Such additional step of heat treating typically results in increased yield loss and part distortion, which is undesirable. Table 1 lists the typical hardness of a variety of relatively high hardness metals produced via PBF-L in stress-relieved and heat treated conditions.
TABLE 1MicrohardnessMaterialGradeTemper(HV)Stainless Steel17-4PHStress-relieved288Stainless Steel17-4PHH900421Stainless Steel15-5PHStress-relieved315Stainless Steel15-5PHH900419Stainless Steel316LStress-relieved203Stainless Steel316L2000° F. for 2 hr171Steel18% Ni MaragingStress-relieved340300Steel18% Ni Maraging915° F. for 6 hr545300SteelH13Stress-relieved613SteelH131076° F. for6531 hr (x2)Nickel-BasedInconel 718Stress-relieved263Nickel-BasedInconel 718AMS 5662408TitaniumTi6Al4VStress-relieved362TitaniumTi6Al4V1725° F. for 45 min316
High hardness and wear resistance in components is desired for numerous applications to increase the durability (longevity) of the components in service. The present invention now identifies alloys and corresponding manufacturing procedures that provide for a layered metallic material, prepared via a layer-by-layer build-up, that indicates a unique combination of relatively high hardness and wear resistance. In addition, such properties can now be achieved by eliminating the use of the above referenced heat treating process applied to existing layer-by layer build-up of known metals. In addition, the properties herein do not require quenching and/or tempering.